Listeria monocytogenes is a gram positive cocco-bacillus which causes perinatal infections and also attacks immunocompromised hosts. Little is known about it in our medium. As part of a prospective study on neonatal systemic infections, its participation at the National Institute of Perinatology was researched. During a period of 18 months, 9,283 live newborns were observed, 141 of them were diagnosed with neonatal septicemia. During this period seven neonates had systemic infections due to Listeria monocytogenes: three had septicemia (two of these with meningitis) and all seven cases had pneumonia. The gestational age of the neonates was 26.1 to 41 weeks (X + DS = 35 + 4.3), with a weight of 830 g to 2,975 g (X + DS 1,958 + 773), four out of seven weighed less than 2,000 grams. The most frequent clinical manifestation was respiratory related causing a need for a differential diagnosis with hyaline membrane disease, transitory tachypnea and meconium swallowing at birth. All of the strains isolated were found to be susceptible to ampicillin, penicillin, gentamicin and amikacin; requiring high CMI levels of cephalosporins.